MEET the brave underwater police investigators from Greenock who dive to hidden depths in their search for answers and helped to convict a notorious killer.

The 12-strong Police Diving Marine Unit based in Greenock is an essential resource in the fight against crime, missing person enquiries and security operations.

The marine unit is deployed whenever an underwater search is required and their work can include anything from retrieving crucial criminal evidence to re-uniting the body of a missing person with their loved ones.

The highly skilled team is capable of forensically recovering items such as weapons and mobile phones discarded by criminals.

Back in 2015, the team's work was crucial in the conviction of a man jailed for life for murdering a student.

The Tele was given a behind scenes look at the team's work.

Police Constable Ross Nielsen said: "It's a job I have always wanted to do since I joined the police.

"I get a lot out of it.

"We are assisting members of the public - someone has got to do that in order to provide closure for the families.

"There's no other job I would want to do."

The team, who are based at Greenock Fire Station, cover as far afield as the Borders, Dundee and Fort William.

To become a police diver, officers must serve a minimum of two years on the beat before undergoing an intensive eight week diving course at the Police Scotland National Dive School, which is also based in Greenock.

Once fully qualified, the officers can dive up to 50m deep, often with no visibility.

PC Nielsen added: "A lot of the time you can't see anything so it's all about touching and feeling things.

"You have got to be fit and able.

"We get a medical and fitness test every year in order for us to continue diving.

"It's got to be a job you want to do.

"It's not for everybody."

The dive team found the spanner that Alexander Pacteau used to bludgeon Karen Buckley to death in the murky waters of the Forth and Clyde canal.

Police constable Steven McKee said: "We recovered the murder weapon and they traced DNA from it.

"It was pivotal evidence."

Sadly, throughout the summer, the unit attended a significant number of tragic incidents.

PC Michael Lodhi said: "Although it might be difficult, as you know what the outcome will be, you're bringing someone's loved one back, you're bringing closure for them.

"You're helping the family.

"It makes it easier for us if you're helping them."

Counselling is always offered to the divers following tragic incidents.

Sergeant Kenny Freeman is keen to make the public aware that it is routine protocol to search water within the perimeters of a missing person enquiry and it does not necessarily mean that someone is in the water.

He said: "A lot of the time it's an elimination search.

"If someone is missing we search the perimeters and if water is included in that then we'll search that area.

"I think when the public see the dive team they immediately think there's someone in the water but it's part of the search."

As well as searches of rivers, canals and the sea, officers in the unit perform counter-terror security sweeps and searches of confined spaces such as culverts, drains and sewers.

They are also experienced in searching ship wrecks.

PC Graeme Wooler said: "We also do ship hull searches and carry out defensive searches for things such as royal visits."

This year, the divers helped out at the European Championship open water swimming event in Loch Lomond.

When the team are not in the water, a lot of their time is spent maintaining their specialist equipment.

Looking ahead to winter, they are keen to remind local people of the dangers posed by icy conditions.

Sergeant Freeman said: "Winter is a time of year when we get quite a number of tragedies involving people going on ice."